This invention relates to programmable devices and more particularly to devices having selectively alterable functional capabilities.
Many systems and devices have been developed and marketed which have the capability to alter, change, or substitute their functional repertoire. That is, the repertoire of the device is changable from one set of functions to a slightly different set. Generally, this is accomplished by emphasizing or highlighting a specific method of handling or procedure normally found in the library functions. By way of example only, the library functions may consist of the numeric functions of addition, subtraction, division, and multiplication. By then modeling the numeric functions appropriately, the repertoire may be expanded to the trigonometric functions of sine, cosine, tangent, and are cosine. Characteristically, a plug-in module, in the form of a magnetic tape, a Read Only Memory (ROM), or Programmable Read Only Memory (PROM), is inserted into the core device consisting of a processor and operator interface. The module will supplement the existing permanent library functions and/or supply needed data so that the new set of functions may be performed. One such application is that of Olander et al, U.S. Pat. No. 4,145,742 wherein the user defines the special functions desired.
Note that the functional capabilties or library functions associated with the processor are determined prior to the insertion of the module. The module simply augments the permanent functions. In this manner, the module sharpens the functional capabilities to a particular field or utilizes the permanent library functions in a particular format or procedure. One example of this is the use of a hand-held calculator's core addition function which may be augmented by a module to perform the iterative summation function symbolized by .SIGMA. (sigma).
The operator typically enters his input via an operator interface which is in the form of a keyboard. This keyboard has, thereon, a plurality of permanently labeled keys, typically switches, to assist the operator in his selection entry. The labels identify the functions of the device.
Since the switches are permanently labeled, the variation of the function set within the core device is severely restricted. To allow some flexibility in defining the function set, blank or unlabeled keys are added to the interface which may then have overlays placed on or near them to physically label them.
Another approach to the problem was that of Wenninger et al, in U.S. Pat. No. 3,971,925. In the Wenninger et al approach, a new keyboard is substituted when the functional set is modified through insertion of a module. The new keyboard, in this manner, has labeled keys appropriate for the new expanded function set of the core device. In this approach, when the module is inserted, so must the keyboard segment be inserted; otherwise, the device is incapable of performing any of the functions associated with the module.